Should I use a moisture barrier under my floor?

If you are overlaying onto concrete with Bamboo, then definitely. This will prevent moisture coming through, otherwise bamboo being a natural product will take some up and it will distort. To doubly ensure on a new pad, a layer of black builders plastic laid first, followed by the underlay to ensure no moisture comes through. If laying on particle board or other wood subfloor we recommend an acoustic underlay to deaden noise.